Yeah, great point here. Facebook really emphasized this difference awhile back when they started allowing users to "Like" a Page, but then choose to hide it from their News Feed.
This allows me, as a Facebook user, to complete my profile and declare that I like something, even if the marketing that the associated Page is doing isn't something I want to see.
This ensures that profile information remains accurate, which is critical for ad targeting - people don't start unliking things they actually like, just to avoid annoying marketing. The interest graph remains intact even when brands make poor marketing decisions.
Do people associate liking things with "completing their profiles"?
Maybe I've been on the other side for too long, but I equate liking a page with opting into their facebook marketing content, and I unlike if I want to opt out.
Yes, that's how FB poses it, as part of your profile. For instance, "What music do you like?" You type in some groups, and that counts as liking them. Suddenly, you get to see news about each concert, blu-ray, etc. they're doing, right in your feed. Not a great experience.
I'm not sure why anyone would assume a very casual social "hey I like X" is equivalent to "subscribe".
People make that assumption because facebook is filled with social people rather than anti-social people who worry that someone they 'like' might actually talk to them.
In normal social circles there an expectation that the you want to hear about things you 'like'. For instance if in real life I have a friend who 'likes' classical music then when I hear something about classical music I will talk to them about it.
Also like is not like subscribe because the idea behind subscribing is that you receive everything. For instance if I 'subscribed' to a magazine I would be rather upset if they only sent me every 7th issue, or only sent me issues when the newspaper had not arrived.
This allows me, as a Facebook user, to complete my profile and declare that I like something, even if the marketing that the associated Page is doing isn't something I want to see.
This ensures that profile information remains accurate, which is critical for ad targeting - people don't start unliking things they actually like, just to avoid annoying marketing. The interest graph remains intact even when brands make poor marketing decisions.